Automatic fuel control for gas turbine engines



May 5, 1953 1J. F. CAMPBELL AUTOMATIC FUEL CONTROL FOR GAS TURBINE ENGINES Filed July 17, 194e 3 Sheets-Sheet l May 5, 1953 J. F. CAMPBELL AUTOMATIC FUEL CONTROL FOR OAs TURBINE ENGINES Filed July 17, 1946 3 Sheets-Sheet 2 INVENTOR. JOHN F CAMPBELL ArrOeA/Evs 3 Sheets-Sheet 5 J. F. CAMPBELL YPASS AREA V 5.` EPM AUTOMATIC FUEL CONTROL F'OR GAS TURBINE NGINES wm Saw May 5, 1953` Filed July 17, 1946 INVENTOR. JOHN F CAMPBELL s n N e m T 7 PPM/moo Patented May 5, 1953 AUTGMA'T'ICQFUEL CONTROL IFGRiGAS.

TURBINE ENGINES-.-

John Fi `Canipbell;"Eclid, 'f1ioassigxjior'-to4 Tlf WeatherlreadCompany, Clevelandfolziiog'fa corporation ofr 01H02.,

Appiicationilulyfli, 1946,` SeriaLNo'. 684,212

Claiinsil (Cl. 15822-3614? L 1 4, The' presentY invention. relates generally. to. fuel flo'winganddistributing means and is .particularly'concerned 'with "novell means for delivering;

liquid'fuelto' a'gas turbine engine;

In the use of 'gas turbineengines, especiallyi.in

aircraft' as .jet propulsioniunits, it 'is critically" important that .thespeed of. the turbine rotor;A which'f largelysietermines` the speed ofthe .ain-N craft; be rapid1'3f"'and .accurately adjustable ac cordi'r'gto. the 'pilotis'. requirements.v Further.- more," it' is desirable` "that ".rot'o'r speed be .auto-.-y mati'cally."maintained constant at any. speed, .'and that""continuous` engine operation. be .'automatically assuredfif de'sired,"regardles`s of thaltitude' andinnnedi'ate engine speed requirementslof the. pilot: The problem is complicated jbcause ,.of.

theI load' upon'suchengines, whic'hconventionallyl,

are"'used to4 drive 'propellers "or centrifugal, air. compressorsor both; variesv widely over alti'- tude range in `whichxtlieengines ,are usedcluetoY the "wide variation in air den-siti? over1that.range. Therefore anwobj'ectof this. invention islto'. pro- H vide meanstwherebythe Aspeediof fthe. rotor olla. gasturbine" engine can' b quicklvpand accurately altered*whilev the engine 'is operating..

Another "object is" to provide' lineans .whereby the 'continuous operationof a gas, turbine. engine. will. be assured, ,if `de`si`red,. underanyl practical. altitudeandengine speed circumstance, andsaid speed willja'utomatically. be maintained constant. at any point. within the'. operating. range-of speeds ofthe engine.

A .iurthe'r object iscto provide means fortaut niaticallitregulatingj. owlof .uidi intra. conduit and preventing flow. in either, .directioniat avrateM in excess of a predeterminedminimum.

A? stilll-v further .object vis 4to i provide .means vfors,

automatically.regulating fluid .pressure i in; :er-.fuel

supplying. conduit. for. an..engine accordance with the-fuel requirements off.theengineatvariefous engine speeds over 'a speedrange rwhereinza. straight line relation does-not:L exist between? en:-VVV gine yspeed and. -vclumelz'oi ffuel'.` frequired; bygfthef;

engi-ne.

Broadly, mysinvention resides invlithe translas-l tionrloifengine:--speedslintoi.pressuresrand- Kthe appicatiorrA or' these`V pressures ftof regulate' auto-f1 matical'lv and/ or f. manuallyA -thef energy inpntrto`-` the' engine-and the speedioi thengnef Referring tov rthe" drawings accompanying and forming partici this specication Figure-'1 diagrammatidally illustrates one .forni^ ci" :speed "regulatin'1g"` meansiof this inventiom'in operating"combination'withagas turbinerengine,"

` tion Acomprises a "fuel source". and. six' functional partsor circuits, viz, fueldeliveringcondu'iifA,L enginebyfpassing circuitsr Band 'C"for bleeding the' .'iuel delivering circuit, circuits D and Efo'rv regulating the nuid now through byfpassing c ircuit' C; and an emergency circuit X for delivering;W fuel tothe engine."

The fuer `sourcel comprises a reservoir (not: shown), a multibranched header I ioiningg the various circuits with'the reservoir .and thusenablinggfuel iiow to 'or vfrom Said circuits; as re, quired'and a boost or Vtransfer pump r2. 'between the' reservoir andbircuits" for impressingwthe header with fuelhydraulic) pressure as4 great as'^275 pis. i. in'emergency circumstancesA and between 'about' 10. 'and 25"'10.V s. i. normal-opera-`v tions." Adjustment of this. punipis manual and isaccomplished by levert.n

The `fueli delivering conduit'` comprises a prn` cipal-conduiteconnecting header!! with the fuel.`

- distributor-Tor the engine, an hydraulic pumpj' geared to the'en'gineyand connected to said Coni duit to'force 'fuel iow therethroughto ,thedi`s`.. tributor," a throttle; `Valve t the conduitLbe-l-- tween .pump 5 and. .the distributonei constant..

pressure' .(700 p. si.) relief valve 7 betweenisaid` throttleland pump for ventingiuelto Ya branch.`

ofsaid header, a4 piston between ,said valve and. the throttle movable" within enlargedcylindrical..

portion@` of the conduit to prevent fuel fion/.between pump 2 'and` the throttle`,.andalventuri. IBv and .,l/"enturi ley-pass valve!! inthe conduit. between said throttlevalve Yand the fuelrldis' tributony. The throttlevalve is connected itosand.. actuated 'by pilotsr lever. |2,.. whichlis vprovidedA withidle stop l3` .to moderately resist movement., of"'said' lelver tdclose said'v'alve.` As' indicatedl thisilever is' disposed 'to` move throughj 90"to1fregulate the position of said throttle valve from.,

closed position. to iull open; and .is limited pin movement vrthrough :15."`tfronrclose` to' ,idlespeed bythe idle'stop.-

Circuit' "Bconsists simply` of 'Conduit I Mii/hitch isI a 'branch' of header" i and spring-loaded Valve It which serves to meter. fuel from thev section of* Lconduitl d between'V the' Vthrottle" and venturi This valve is sprung against movement to permit fuel iiow through this by-pass circuit and is disposed to permit such flow only when pressure within said conduit section exceeds 65 p. s. i. Because of the peculiar profiling of this valve, the reason for which will be fully set forth below, increases in fuel pressure urging valve movement to compress spring I6 at iirst bring increases and then decreases in the orifice area until the valve is finally closed at 340 p. s. i.

The second by-pass circuit (C) comprises a conduit I'I having two enlarged cylindricallyshaped portions I8 and I9, and connecting the section of conduit 4 between valve I5 and the venturi with header I, and piston valves 2U and 2I within said cylindrically shaped portions for metering flow of fuel through said by-pass circuit by movement within cylinders I8 and I9, respectively, in accordance with the dictates of regulating circuits D and E, respectively.

Circuits D and E actually are two circuit pairs, one of which pairs constitutes circuit D and acts to position valve and regulates its orifice area, and the other of which pairs constitutes circuit E and acts to position valve 2I to regulate its orifice area.

Circuit D comprises a conduit 22 connecting header I with an end of cylinder I8, a pump 23 between said header and cylinder for developing an hydraulic pressure in said cylinder and upon piston valve 20, a flow control valve 24 in the conduit between pump 23 and the cylinder, which is insensitive to pressure differences across it but acts in response to fluid flow to impede or entirely prevent such ow depending upon the tendency for that flow to occur, and a constant pressure 350 p. s. i. relief valve 25 between the pump and iiow control valve for bleeding the circuit and limiting the hydraulic pressure within it. Pump 23 is geared to the turbine and even at idling speed has a capacity greater than necessary to maintain a pressure in conduit 22 in excess of 350 p. s. i.

Circuit D further comprises means for developing a pressure upon piston valve 20 opposing that developed by aforesaid portion of the circuit. This means includes conduit 26 connecting header I with the end of cylinder IB opposite the end thereof opening into conduit 22, a pump 21 between said header and cylinder for developing an hydraulic pressure in said cylinder, manually adjustable engine speed selector valve 28 between said pump and cylinder for bleeding fuel to header I from conduit 26, and a constant 450 p. s. i. relief valve 29 between pump 21 and selector valve 28. The speed selector valve is actuated by the said throttle lever and is opened and closed when the throttle is opened and closed by the pilot.

Circuit E comprises a conduit 39 which connects one end of cylinder I9 with the portion of by-pass conduit I'I between the valve 20 and conduit 4. It further comprises a conduit 3I which connects the opposite end of said cylinder to the throat of venturi I0 and a spring 32 within the cylinder and extending between the piston valve and said opposite end of the cylinder. The conduit 3I communicates with cylindrical portion 9 of conduit 4 and is adapted to transmit Venturi throat pressure to cylinder I9 in normal operations and to be prevented from thus functioning by movement of piston 8 in accordance with emergency operating conditions.

The emergency circuit comprises, in addition to the transfer pump 2 and header I, a branch 33 of the header Which opens into -conduit 4 in the section before the throttle valve and by-pass valve I5, the portion of conduit 4 between said opening and the fuel distributor, and a throttle valve 34 in said branch. Aforesaid piston 8 in normal operation is disposed to prevent flow of fuel to throttle valve 34, and in emergency operation is disposed to permit such iiow and to prevent fuel flow from pump 5 to throttle walve 6. Throttle valve 34 is actuated by lever I2 and due to the arrangement of the system, engine operation is entirely manual, the automatically operating circuits being blocked and prevented from exerting any effect upon the fuel delivery rate to the distributor.

Referring now to Fig. 3, it will be seen that required total by-pass area in square inches is plotted against engine revolutions (thousands per minute) for various altitudes including sea level, 5000 ft., 10,000 ft., 20,000 ft., 30,000 ft., 40,000 ft. and 50,000 ft. The result is a family of solid line curves graphically illustrating the relation existing between engine fuel requirements and speeds under any speed or altitude circumstances from Zero to 12,000 revolutions per minute and from sea level to 50,000 ft. Also plotted on the chart is the effective by-pass area of valve 20 under the various aforesaid altitude and engine speed circumstances. 'I'he result is the illustrated, appropriately labelled family of dotted line curves subtending to varying degrees, the corresponding solid line curves. The chart also bears a dotted line curve, indicating the safe maximum by-pass area over the operating range and labelled Safe Max.; and another dotted line curve labelled Burner Blowout which indicates the total by-pass area over the operating range when fuel combustion ceases.

The total by-pass area over the full speed and altitude range is accounted for by valves I5 and 20. Thus the area defined between the dotted line curve for any altitude, representing the bypass area accounted for by Valve 20, and the corresponding solid line curve is accounted for by valve I5 which is appropriately profiled to produce this effect. The values set out of this chart are not to be construed as absolute or quantitative, or as imposing limitations upon the appended claims, and the relationships indicated are to be understood as qualitative only.

In the operation of the system illustrated, under normal circumstances, fuel is drawn from the reservoir and forced into header I by pump 2 under a hydraulic pressure of l0 to 25 p. s. i., which is depicted by the number (it) signs. A portion of this fuel is forced by pump 5 through conduit 4 past throttle valves and flowed to the fuel distributor and engine combustion chamber after receiving the controlling and modifying effects of by-passing circuits B and C. This flow of fuel to the combustion chamber is indicated in Fig. l by dots and is,of course, proportional to the speed of the engine at the outset of its travel through principal conduit 4. The fuel is iinally delivered to the engine in accordance with the pilots desires and according to requirements of safety which are automatically enforced by the system. Thus at constant speed a particular pressure schedule obtains in the principal conduit, and while in different portions of the conduit pressures are different and iiow rates are increased or diminished, combustion chamber operation proceeds at a practically invariable rate and engine speed is accordingly invariable.

aeavgeva 1 x ther; portionsn'fr'` fuel inlsaidiheaderarefforced fbyfpumpwZ 3 into lconduitaZ 2fandfby` pump 2 l1 finto' conduit-f 2 6 and :rare f `regulated Vrin,y ytheir flow by; valves -4.2 v and 1 28;- -respeotivelyirv Theopresence of fuel undery pressure Lin 'these conduits is indicated 5 in Fignlby the' plus signs :(r-i- .5 Obviously; since f there is no means-exceptvalve 2`51'for1venting fuel from fconfzluit-A 22, l. fuelfrrilowf: through thatzxvalve must@ occur constantly: and@ infrvolume equal to that delivered: byfthe pumpizf with the excepel tion that` negligible avolumevchangesin .1 the sysu tem 1 occur becauseof achangesfindisposition: of l Valve `2i): At" constant:v engine speed there Aiis; also i obviously; a` continuous floWf-l from, .conduitl' 2E throughr Hvalve '28,@ corresponding iin volume lto i thatfdeliveredby pump? 1.-: v

Asa fori the.; disposition:- of the-ff above described: parts affecting:V the, `fuelpfiflow!A ini `such :constantrl speed operation; alliare substantially. etation'ary andlthe flowithrough'mtheA by=passingl circuits (B' andffC) is r constant, .pressure being-L balanced. across the various valves 1.5,! 2G `and12 I Y Assumingithat the pilot `"desires toxincrease en# gine'A speed andradjusts thelcontrolalever i2 .ae-ficordingly, the .aforedescribed equilibrium situa-` tioni is .destroyed'l'and theoperations'of the 'sys-k temiand the :disposition 'of many voffits' moving parts :undergoes aiy considerablechange.` First, movementof 4said lever to increaseiengineuspeed` causes movement. of the i throttle L6 to 'allow` more fuel l:to iiowiithroughthe' 'principalfconduit and causesy :movement-ty of speed" selector valve 28 1- in theropposite direction resulting in the by-passing of a-greater volume'of fuel I'from conduitZi.v For the-'moment only-,enginelspeed remains unaf` fected: `and`v unchangedig but withthe vincreased now i fof fueliy fromI conduit V.2,6 --tc 1 the-header,A the hydraulictpressure `iwithinthe conduitA diminishes and valve 2li moves in accordancewiththeicon-f stant pressure exerted*through'wcondu-it 22 and closes to some extentor entirely, thus decreasing or preventing flowv of fuel through bypassing circuit C. Greater ow' of fuel to theidistribu'tor and combustion chamber. ensues alrn'ostA :immediately and the `gas pressure developed inthe combustion chamber is constantly.. increasedl andthe pressure exerted upon theturbineengine' rotor-'is increasedoaccordingly,aas; is the'speedfof therein-"b gine. With the increase .in engine 'speed-there iin-- mediately results an corresponding increase-inf the speed of the .purr-:psi 23 1and27.; Obviously, one effectofxthisipump speed increasevfis toovercome-v l the pressure-reducing. effect :of the increased: orice described :byfvalve 28ifa-sfa resu'ltof aforesaid movement; of control lever i 2, andto increase the hydraulicpressuresin .conduit 25,to cause movel ment .of valve 20 oppositel-to the influence lof the constanthydraulicpressure (350p. s. i.) carried in conduit 22. This movement Vofivalvev 2i? continues until balance betweenthehydraulic-.pressures applied againsttheopposedvsides of the-pis-` ton is established and .fuel-flow through the bypass-*circuit is restored at thef--rate necessary to v maintain fuel yflow'ito thei fuel.. distributork at `the 1 level required for the engine speedidesiredbythe pilot, as indicatedby the settingloflever 1.2;#

On the other hand, if the speedioftheengineis to be reduced in accordance With-,pilotsrequi-re ments and lever l2 is accordingly -disposedito 1aecornplish this, the rsteifect isto'simultaneouly decrease thevolume of fuel-supplied to the `L distributor rper time unit1, byclosing the-throttle valve 6, and to increase-thepressurefschedulel iny conduit 26'by restricting the orifcedescribedby valve 285i It will ibeobvious ithatimovement .iof 75 io higher speed ranges, since it will'relieve the pres sure against `the yspring -load' of that valve an allow it to move towardlitsnormallyfclosedlposi tion, but-only to the pont1at, which'l thativalveisw openr` to the greatest extent. Theseeectssoii` course, wllliall be reflected in a considerablefza'nd':14

very abrupt decrease in the volume of fuely deliv' ered i to'y the"I combustion f chamber,ffand` consequently, in a corresponding decrease in thevgas pressure applieduto the-.turbine rotor. Turbin speed .will thereupon 'abruptly decreaserand-'pump' 5, 23 and linthe various circuits *of this' sys i tem willv correspondingly.decelerate Theec -1 in the principal conduit will-not l'beparticu'lairlv"l important so far` asthe volume 'ofiy fuel Veffluent" l'o the'y distributor is concerned-,1 becausetheavariousvolume controlling thel valves aforedescribedwill have `already and willI continue to determine that?"l volume regardless of 4pump 'Theachangesin speed of pump 23 likewisewill be unimpor n inasmuch as at'any turbine-speedihydraul-icfpres sure is maintained in conduit 22at1a constan f value, that is, 350 pps-1. becauseof'the aforo f mentioned constant `pressure -valve.=1 Changer in? speed of the pump supplyinghydraulicpressurey to conduit 25,1is however, very noticeablefand'iin-i portant inasmuch as'it reduce'sthe -pressurevap plied against the valve 20 by bringing thevolum' of fuel delivered kby .that pumpintoagreement, as far Ias quantities are concerned; with thevolu'rn'e ff byepassed `by valvel28. -YValve Zlthenisgradua broughtfinto `an equilibrium'- lposition` as the con stant lpressure appliedA by the constantlpressure'i circuit (conduit 22, etc.)"andthe-variablepres sure applied bythe variabler pressure'circuit (con duit .26, etcbecome equal 'at'Ia-point-lwhic allows fuel. now throughthe by'-passllineini'acevv cordanee with the enginevandaircraft,'speed reff' quirements ofthe pilot.

If engine speed fis abruptly fde'creasedwhroug a considerable range-lor if thevdecreasefoccur in certain altitude ranges where burnerblcw out is likely to occur-Witlimoderate speedffde creases,fuel combustion has a tendency tosto' Such .failure of the power source 'is dangerous `be cause rekindling burners is ordinarily. impos sible for a long period afterfoperation inlfthei higher speed ranges, 'especiallyfund'er ifliglit'coni# f ditions.` The afcrenientionedfseeondfbyl-pass fi'o'w control circuit E is thereforeiprovidedandl'opw crates to maintain fuel tofthe combustionchani-. ber above-minimum safe ioperatingulevels-Dur r ing.' normal operation',A when-*equilibrium obta" in thelsystem, valve 2| is notidisposeditointer fere with fuelifioivthroughthovby-passicircui The Vsaine situation prevailsYfwhen-the #engi accelerated 'and the fuel flowthrough 'the prin pal' 'conduit is increased-icorrespondingly. 'How-#1i ever, when the schedule -of yfuel delivery `toth combustion chamber is decreasedflandiespeciallyf'- when it is decreasedover a considerablerange of pressures,v valve'Z i- 'overrulesl valvefZUl'whic as explainedlis thendisposed to permit `-rapid' fio" offuel through the by-pass line, and valveZ I` subd stantially prevents or drastically-limits fuelfiiow through .that line; depending uponf the/'proximity of the pressure in the principal conduit to dangerously low levels. By way of example, assuming that flow through venturi I falls to a relatively low value, the pressure in conduit 3|, which is indicated in Fig. 1 by the triangle (A) signs, is thereby correspondingly increased in accordance with well known uid flow principles and the valve 2| is unbalanced, the pressure urging its closure being greater than the pressure tending to maintain it. Spring 32 is carefully adjusted in order that delicate balance of opposing pressures across the piston of valve 2| may be obtained and in order that closure of the valve will occur when control afforded by that Valve is essential to continued safe operation of the turbine engine. In the higher speed ranges, of course, the pressure developed in conduit 3| is relatively small due to the rapid rate of ow of fuel through the Venturi throat. Under this circumstance the valve, of course, remains in its open position and does not interfere with the dictates of valve 2| as to the fuel flow schedule through the by-pass line.

In the event that the speed of the engine is sufficiently great to cause the establishment of a pressure in the principal conduit and upon valve I5 in excess of the pressure required to cause opening of that valve against opposition of spring I8, and to cause fuel flow from the principal conduit to header an adjustment to increase the speed of the engine will cause movement of the valve further in the direction against the spring load. Depending upon the degree to which the valve has thus been moved, there results an increase in the volume of fluid bypassed by means of that valve, or a decrease in that volume.

It will be noted that valve |5 is profiled in a particular and novel manner and that valve 20 is profiled in a substantially opposite manner to meter flow of fuel from the principal conduit. These proles are carefully matched to establish the necessary by-pass area for any given engine speed and altitude circumstance. Since the pump 5 is geared to the engine and operates at a rate corresponding to that of the engine, and since in some altitude and engine speed ranges the capacity of the pump is too great to maintain a given engine speed, provision must be made to compensate for the differences. other words, the pump output under certain circumstances is greater than the fuel iioW requirement and itis necessary to provide by-pass means functioning oppositely to the dictates of the valve 20, which is profiled generally as though a straight line relation existed between engine speed andengine fuel requirements.

The necessity and function of this second bypass valve and circuit is readily appreciated upon consideration of Fig. 3 which clearly illustrates the typical humped curve defining the fuel efficiency of the engine over a range of speeds. The efficiency, in other Words, varies with speed so that the amount of fuel required per revolution decreases with increases in speed to a point of maximum eiciency and then increases with increases in speed. As a result, at any given altitude the total by-pass area in the fuel delivery system must increase with increases in speed to a point of maximum engine efficiency, and then decrease With further increases in speed in order that engine fuel requirements can be met. At higher altitudes the total by-pass area must increase with increases in altitude because with a vconstant throttle setting, the engine R. P. M.

tends to increase because the load upon the engine is lessened due to the lesser density of the atmosphere. Obviously no single valve responsive only to pressure impulses, such as valve 20. can be suitably profiled for use over the entire speed range of the gas turbine engine because such a valve would, under certain circumstances, function to increase the flow of fuel to the engine when the opposite effect was desired as indi-l cated by the direction of throttle movement, and would function to decrease such flow when an increase of such fiow is desired. For instance, assume that profile of valve |5 is superimposed upon profile of valve 20 to define the by-pass area necessary, as indicated under any sea level engine speed circumstances set out in Fig. 3, and assume movement of the throttle to decelerate the engine from 8,000 to 5,000 revolutions per minute. Reference to the sea level solid line curve of Fig. 3 indicates that a decrease in the total by-pass area is necessary but it will be obvious that movement of valve 20 resulting in such decreases can result only in increase in speed of the engine. The operation of circuit D is such that to accomplish decelaration it is necessary to displace valve 20 to increase the by-pass area and permit more fuel to by-pass the engine. It is clear that operation in this assumed manner could therefore result only in increase in the turbine speed, contrary to the dictates of the throttle lever, and a progressive increase in the speed of the engine due to the increase in output of the pumps 5 and 21 and the resulting continued movement of valve 20 to further restrict the by-pass area and to cause progressively greater volume of fuel ow to the engine. Valves I5 and 20 are therefore provided and they are arranged to compensate automatically for these variations. in engine fuel requirements.

At the point of maximum efficiency of the turbine engine, valve |5 floats in such a way that a maximum of by-pass area is defined by the valves l5 and 20. Movement of the throttle lever to increase or decrease engine speed causes an increase or a decrease in the pressure against valve |5 exerted by fuel in conduit 4, which results in movement of valve |5 to decrease by-pass area. When the throttle is advanced, the fiuid (fuel) pressure upon valve l5 is increased and the valve is urged against spring I5; movement of the throttle to decrease engine speed results in relief to an extent of huid pressure on valve l5 and movement of said valve in response to urging of spring I6.

As to operating the system under emergency circumstances, transfer pump 2 speed is manually increased by appropriate movement of lever 3 and fuel is delivered into the header under 275 p. s, i. pressure, which is indicated in Fig. 2 by the asterisk` signs. Displacement of the emergency circuit control piston 8 immediately results and opens the Way for fuel flow through arm 33 of the header, past manually operated throttle control valve 34 which is actually a part of throttle 6, and thence through the venturied principal conduit 4 to the fuel distributor and combustion chamber. Fuel thus throttled is depicted by the Greek letter phi (e). Pumps 5, 23 and 2'| continue to operate, being geared to the turbine engine, but their effect is not felt either in regulating the rate of ow of fuel to the fuel distributor or in actually causing fuel to flow through the system to the distributor. This is because valve 2| is moved to the closed position by pressure in line 3| as a reduit 33. by-pass circuit vC, Athe :position of' valve'zll in :response to pressures Ifromcontrol pumps 23 and 5 and by-passing said engine, means for `varying to prevent flowA of fluid through the Fconduit whenever Athe `tendency yior ignited therein. vented from the chamber to the turbine 'rotor bly. liunder substantial pressure into the combustion lchamber in an Vamount substantially in excess of .moeren visult "of .,movemem;lofxemergency: control piston 8 to the right under actionfiofipressuretin con- 4,Since valve.2lhas.moved to close. oi

21` has `no effect onv fuel iiow. Valve I5 is :likevwise disposed in .closed 'position as a result of being subjected to thetransfer pump hydraulic pressure in line lll, which pressure is resisted only .by the lesser hydraulic or throttled presfsure in that portion of the 'principalrconduit 4 ldisposed betweenv the fuel distributorand Athrot- A.tle valve 34. There is, as a result, no -iiowof `fuel .through by-pass circuit. B, and since by-pass circuit C has `been closed by valve 2l, `manual.`

control of pilot line :I2 alone 'determines .the frate' of `flow of fuel to .theengine The pressure at which the fuel reaches the fuel-distributor is indicated in Fig. 2--by thephi (eisigns,

4and this pressure determines speed of the engine. Obviously, there are various eouivalentmeans of accomplishing applicants purposes and other .combinations of the means depicted and -de- .scribed herein. but `these are contemplated by the appended claims wherever the departure from this disclosure is not material.

Other means than the ow control 4valve 245 Vmight be employed to eliminate or .minimize surging in the constant pressure circuit and to -maintain the proper rate of travel of valve Zt and minimize disagreement between actual and permitted rates of change of speed `of the enzgine. Valve 24 comprises a generallyG-shaped vmember Adisposed between springs 35 ande@ for .movement as aforementioned within conduit to A-regulate fluid` flow'through conduit by engaging, through either point of the C, the annular n in vsaid conduit or by moving tovvard or away from such `an engagement. .As illustrated `in Figs. 1 and 2, thisvalve is ble of `making afluid tig t Acontact withthe in'feither vdirection such flovvbecomes greater than. a predetern .mined-mimimum for which springs and se are adjusted. The various pumps or any of them might be driven by-other power sources lthanthe i turbine, in which case appropriate circuits could be evolved from the teachings .thereof without departing from thespirit of lmy invention.

Fuel,-delive1ed tothe combustion chamber o Ythe turbine engine. by the foregoing means is The combustion are which drives the air-compressor of *the assem- The air `compressor therein .delivers fai-r 'the stoichiometric requirement for vcomplet-e osi dation `of the `uel. The excess of air assistsl `propulsive effort of the Aturbine and the jet :through vwhich the. gases` are broken `down Aand tion or design.

.The pressures stated herein arev offered for Epurposes of illustration .only andare not 'tov be construed as imposinglimitations upon the appended claims `in any respect.

:Having thus describedtbe' present invention, I. state that what .l vdesine to secure by Letters Patent -is `defined vin whatl is claimed,

, @L10 What is claimed is: 1. 'Fueldelivering meansor agasturbine enginefcornprising a fueldelivery conduit,a by-pass conduit bleeding said fuel `delivering conduit the rate of'oiv of fuel-through said by-pass conduit izo-effect u'desired changes in engine speed :including a yvalve inV saidby-pass conduit po- `sitfionable -to regulate `the 'flow of fuel therethrough, and means for automaticail" maintaining the ratey of flow of fuel through said liuelf delivery :conduit abovef a predetermined 'minin'iumf,:rsaid :last-named -means including a second-valve insaidiby-pass conduit. means vto losesaidfsecond valve when the fuel flow in said deliveryconduit falls below a predetermined .,minimum, closing vof Y said second valvev comm pletely closing` said `icy-pass conduit.

2;-` Fuel delivery means for a gas turbine engine comprising-'a fuel-delivery conduit, a second conduit'bleeding said fuel' deliveryV conduit Vand vbypassing said engine, a `free-'floating valve in said second conduit positionable to adjust the rateV of fuel flow therethrough, means vfor positioning said *valvefincludingmeansfor developing a substan- :tially rconstantluid pressure urging movement of 'said'valve in oneldirectionto decrease said rate and-'means ffor developing a fluid pressure l which varieswith `engine speediurging the` valve inthe other-'direction to increase said-rate, said variable `and'constant pressures 4balancing' said noating vpistonl at constantv4 engine speed, and control *means to 'Varyf'said variable `pressure yindepend- 'entlyof engine speed.

" 3; Fuel delivery meansfor a gas turbine engine 'comprising aef-uel conduit, a second conduit bleedingsai'd fuel delivery 'conduit andby-passingfsaid lengine, :means for causing fuel'flow throughsaid conduits including a pump arrangedto be driven bytherenginef afmetering valve infsaid second yconduitpositiona'bleftoadjust the volume of fuel by-pa'ssing the engine, 'means `for positioning said 4`valve :including means forf developing a substantially constantluid pressure urging movement votsaidvalve in'one direction to decrease said volume-fand' means for developing a fluid pressure which varies' with' engine speed urging the Valve iii/"the other `direction to increasey said volume, 'saidvariable and constant-pressures balancing 4said valveat constant engine speed,'and control 'meansto Avary said *variable pressure independ- ="ently' O'engine speed.

4: `:Fuel delivery means for a'gas turbine-engine comprising a valvepositionable'to adjust the rate oideliveryof-fueltosaid engine, and means for 1ciositioningsaid` valve, said l positioning Vmeans inv'cludin'g meansfordeveloping a substantially con- `stantpressureiurging `movement of said valve in one directionto increase said'rate and means ini-cluding'an hydraulic pump arranged to be driven bythe engine for `developing pressure which varies with engine vspeed'urging said valve in the other "direction togradually decrease saidfrate of fuel i'flow, said variableand constant pressures balancingfisaid valve at 'constant engine speed, Vand means i`orvarying said 'variable pressure inde- `pende'ntly'of Vengine speed comprisingfmanually `.controllable meansfor bleeding thepressurede- Avelcped by saidfhydraulic pump before itv reaches V:said valve.

V5. Fueldeliverymeans for a gas turbine engine comprising a fuel delivery conduit having a branch connected to said engine and two branches fby-passingosaid engine.' a;-piston lvalve in `one of said branches positionable to adjust the rate of fuel oW therethrough, means for positioning said valve including means for developing a substantially constant fluid pressure urging valve movement in one direction to decrease said rate and means for developing a fluid pressure which varies with engine speed urging valve movement in the other direction to increase said rate, said variable and constant pressures balancing said piston at constant engine speed, control means to vary said variable pressure independently of engine speed, and means for adjusting the rate of fuel flow through the other by-pass branch including a pressure sensitive metering valve.

6. Fuel delivering means for a gas turbine engine comprising a fuel delivering conduit having a branch for delivering fuel to the engine, and tWo branches adapted for by-passing the engine, and a hydraulic pump arranged to be driven by said engine, and disposed within said conduit for causing fuel flow through said conduit. a piston valve in one of said branches positionable to adjust the rate of fuel flow through said branch, means for positioning said valve including means for establishing a substantially constant fuel pressure urging valve movement in one direction to decrease said rate, and means for developing a fluid pressure which varies with said speed urging valve movement in the other direction to increase said rate, said valve and constant pressures balancing said piston at constant engine speed, and control means to vary said variable pressure independently of engine speed, means for adjusting the rate of fuel flow through the other by-pass branch including a pressure sensitive metering valve profiled to compensate for discrepencies between engine fuel requirements and fuel pumping capacity of said hydraulic pump at varying engine speeds.

'7. A system for delivering fuel to a gas turbine engine comprising an engine feeding line. a line bleeding said feeding line and arranged for bypassing the engine during normal operation, a normal fluid circuit for supplying said feeding line with fuel and an emergency source of fuel under pressure connectable to said feeding line, said normal circuit including a control valve positionable to adjust the rate of flow of fuel through said by-pass line, and an emergency ,l

fluid circuit including means for connecting said emergency source to said engine feeding line and means for preventing flow through said by-pass line upon operation of said connecting means.

8. A fuel feeding system for a variable speed engine comprising a fuel supply pump arranged to be driven at a speed proportional to engine speed, fuel supply means for said pump, a fuel delivery conduit for conducting fluid from said pump to the engine, by-pass conduit means connecting said delivery conduit to said fuel supply means, and regulating means for controlling fuel flow through said by-pass means, said regulating means comprising a profiled by-pass valve for controlling flow through said by-pass conduit, means for urging said by-pass valve in on'e direction with a substantially constant force, means for urging said by-pass valve in the other direction with a force that is a substantially linear function of engine speed, any difference between said forces tending to open the by-pass Valve as engine speed increases, means to manually adjust the force of one of said means acting on the by-pass valve, said by-pass Valve being substantially free-floating with respect to said 12 opposed forces and balanced with respect to fluid in the by-pass conduit.

9. A fuel feeding system for a variable speed engine comprising a fuel supply pump arranged to be driven at a speed proportional to engine speed, fuel supply means for said pump, a fuel delivery conduit for conducting fluid from said pump to the engine, by-pass conduit means con necting said delivery conduit to said fuel supply means, and regulating means for controlling fuel flow through said by-pass means, said regulatng means comprising a by-pass valve for controlling oW through said by-pass conduit, means for urging said by-pass valve in one direction With a substantially constant force, means for urging said by-pass valve in the other direction with a force that is a substantially linear function of engine speed, any difference between said forces tending to open the by-pass valve as engine speed increases, means to manually adjust the force of one of said means acting on the bypass valve, said ley-pass valve being balanced with respect to fluid in the by-pass conduit, and compensating by-pass means responsive to fuel pressure in said fuel delivery conduit arranged to bypass a maximum quantity of fuel at an engine speed where fuel requirements per revolution are a minimum and to by-pass a lesser quantity at both greater and lesser speeds.

1Q. A fuel feeding system for a Variable Speed engine comprising a fuel pump arranged to be driven at a speed directly proportional to engine speed, fuel supply means for said pump, a fuel delivery conduit for conducting fluid from said pump to the engine, by-pass conduit means connecting said delivery conduit to said fuel supply means, and regulator means for controlling fuel flow through said by-pass means, said regulator means comprising a by-pass valve in said by-DaSS conduit, a source of fuel at constant pressure tending to close said by-pass valve, a source of fuel at a pressure proportional to engine speed tending to open said by-pass valve as engine speed increases, and means to manually adjust the pressure developed by one of said pressure sources, said by-pass valve being balanced with respect to pressure in said by-pass conduit.

11. A fuel feeding system for a variable speed engine comprising a fuel pump arranged to be driven at a speed directly proportional to engine speed, fuel supply means for said pump, a fuel delivery conduit for conducting fluid from said pump to the engine. by-pass conduit means connecting said delivery conduit to said fuel supply means, and regulator means for controlling fuel flow through said by-pass means, said regulator means comprising a by-pass valve in said by-pass conduit, a source of fuel at constant pressure tending to close said by-pass valve, a source of fuel at a pressure proportional to engine speed tending to open said by-pass valve as engine speed increases, and means to manually adjust the pressure developed by one of said pressure sources, said by-pass valve being balanced with respect to pressure in said bypass conduit, second by-pass means for connecting said delivery7 conduit to said fuel supply means, a valve in Said second by-pass means arranged to by-pass a maximum quantity of fuel when the engine is operating at its most enicient speed, said second by-pass means being arranged to by-pass a reduced quantity of fuel at other speeds.

l2. A fuel supply and regulating system for a Variable speed engine comprising a source of fuel under pressure for said engine, a by-pass for said source of fuel, a first valve in said by-pass engine speed responsive governorI means including an engine speed responsive device for said rst valve controlling the flow of fluid through said b'y-Dass, means for manually adjusting the governor means to produce a predetermined engine speed, a second by-pass for said source of fuel, means for controlling fiow through said second by-pass comprising second valve means responsive to fuel pressure in said source, said second valve means being in maximum by-pass position at intermediate fuel source pressures and at reduced by-pass positions at higher and lower fuel source pressures in order to compensate for discrepencies between engine fuel requirements per revolution at various engine speeds.

13. A fuel supply and regulating system for a variable speed engine comprising a source of fuel under pressure for said engine, a by-pass for said source of fuel, a rst valve in said by-pass engine speed responsive governor means including an engine speed responsive device for said first valve controlling the now of fluid through said ley-pass, means for manually adjusting the governor means to produce a predetermined engine speed, and means responsive to fuel flow to said engine for closing said by-pass when fuel flow reaches a predetermined minimum, a second by-pass for said source of fuel, means for controlling new through said second by-pass comprising second valve means responsive to fuel pressure in said source, said second valve means being in maximum by-pass position at intermediate fuel source pressures and at reduced by-pass positions at higher and lower fuel source pressures in order to compensate for discrepencies between engine fuel requirements per revolution at various engine speeds.

14. For use with an internal combustion engine, a fuel regulating system for automatically maintaining engine speed constant by controlling the fuel supply of the engine comprising a fuel supply pump with an outlet pressure proportional to engine speed, an engine feeding line leading from the pump to the engine, Valve means having a connection to said engine feeding line to modify the pressure in said engine feeding line, a separate control system for said Valve means comprising means driven by the engine and connected for positioning said valve means to modify fuel pressure in said engine feeding line as engine speed varies from a selected speed, and compensating valve means to further modify said pressure and compensate for the non-linear relationship between the fuel supply from said pump at a given engine speed and the fuel requirement of the engine at that speed, said compensating valve means being connected to said engine feeding line and arranged so that it is in intermediate position at intermediate fuel line pressures upon which a minimum quantity of fuel is allowed to pass to the engine by the valve, an increase or decrease in fuel line pressure increasing the fuel allowed to pass to the engine by the valve.

15. In a gas turbine, a fuel supply system comprising an engine feed line, a source of fuel under pressure for said engine feed line, a venturi in said feed line, and automatic means for controlling the fiow of fuel in the feed line including a valve in said fuel feed line and an engine speedresponsive governor for controlling said valve, a burner blow-out protective system comprising auxiliary valve means connected to said feed line and movable to increase fuel pressure in said feed line independently of said automatic controlling means, and a pilot line leading from the throat 0f said venturi to said auxiliary valve means arranged so that pressure increase in said pilot line causes the auxiliary valve to move to increase fuel pressure in the feed line, whereby a reduction in fuel ow through the venturi below a predetermined minimum causes pressure in said pilot line to increase and the auxiliary valve operates to maintain fuel flow in said venturi at said minimum value.

JOHN F. CAMPBELL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,854,722 Tarisien Apr. 19, 1932 2,330,558 Curtis Sept. 28, 1943 2,405,888 Holley, Jr Aug. 13, 1946 2,407,115 Udale Sept. 3, 1946 2,440,371 Holley Apr. 27, 1948 2,446,523 Bradbury Aug. 10, 1948 

